Fixed obstacles on the road, such as tollgates, roadwork sites, accidented vehicles, and road maintenance workers, are equipped with various devices designed to make them easily visible, especially in the dark or in particular environmental conditions, such as fog, snow or rain.
Currently available equipment essentially consists of active or passive visual devices, such as signaling lights, reflex reflectors, and warning triangles.
In conditions of particularly low visibility, this equipment may be inadequate, exposing the road user to serious risks of accidents.
U.S. Pat. No. 4,440,104 discloses and claims a warning triangle device, having retroreflective and fluorescent arms, which increase visibility thereof when lit up.
This prior art arrangement has the drawback that the effectiveness of the retroreflective material is dependent on the intensity of the light source that lights it up. In the event of low visibility, such as in fog conditions, the light source, e.g. the headlights of an approaching vehicle is partly attenuated, and so is the reflected signal. The light beam passes through the light-emitting means twice, i.e. from the approaching vehicle to the reflective material and from the reflective material to the observer.
A further drawback of this device is that, in low visibility conditions caused by fog, if the approaching vehicle uses upper beams, the light reflected by the fog causes an excessive diffused lighting, which may dazzle the driver. However, if the driver properly uses fog-guards, which are normally downwardly and sideways directed, the warning triangle is seen at the last moment.
U.S. Pat. No. 4,875,028 discloses a safety triangle which has, in addition to a retroreflective surface, an inner portion with red or yellow light sources. This device uses the power of the car battery, through a DC connector to be connected to the cigarette-lighter socket.
In addition to the disadvantages as set out above, such prior art device has the drawback that it has to be placed on the vehicle, e.g. on the roof, due to the power supply arrangement, to provide a signal that is eventually untimely, especially in low visibility conditions.
An additional shortcoming of this triangle is that, in case of prolonged usage, it may discharge the car battery, thereby causing serious damages thereto.
From U.S. Pat. No. 6,515,584 a safety device is known, onto which blinking lights are mounted that produce a rapid pattern of short light pulses, followed by a more or less long pause.
This prior art arrangement has the drawback of dazzling the driver, the light source having a very high intensity. Furthermore, it has a very complex light control arrangement, which requires a high battery power absorption, whereby batteries tend to discharge rapidly, which makes the device unusable in case of prolonged usage.
Other emergency warning devices are known from U.S. Pat. No. 5,512,876, EP 089852, and EP 0691243.
These devices are also of little use, especially in low visibility conditions, as they generate a very low-intensity light beam.
Generally, all the above prior art arrangements have the drawback that, to provide an effective emergency warning signal, the user has to place the device at a very short distance from the stopped or disabled vehicle, as prescribed by applicable rules, and is thereby exposed to danger.
French patent 2,816,264 discloses a visual signaling device mounted onto a vehicle, which is based on the use of laser beam projection, providing effective visibility properties in low visibility conditions.
However, no attempt has been made heretofore to include a laser light source on a fixed signaling device like a warning triangle.